With the improvement in CT scanners and injectors, diagnostic chest CT can now be performed in less than 10 seconds. It was hypothesized that diagnostic CT pulmonary angiograms could be done with less than the usual 80-120 ml of contrast used. We have developed a method of performing diagnostic CT pulmonary angiograms with 30 ml of intravenous contrast in most patients. The long-term objective of this study is to show that there is no difference in the diagnostic efficacy of this low dose 30 ml technique when compared to the more traditional full-dose technique.